Oxygen concentration detector

Abstract

The present invention relates to an oxygen concentration detector to be used in a system which can simultaneously dispose of the three harmful elements in automotive emissions, i.e., unburnt hydrocarbons (unburnt HC), carbon monoxide (CO) and nitrogen oxides (NOx) through reaction with catalyst. In said detector an oxygen concentration cell comprises a solid electrolyte of a special ceramic material characterized by oxygen ion-conductivity; and the oxygen concentration of a measured gas can be analyzed by measuring the electromotive force generated through a difference in the oxygen partial pressure between the measured gas and a reference gas.

What is claimed is: 
     
       1. A vehicle exhaust gas oxygen concentration detector comprising: (a) a solid electrolyte vessel made of a ceramic material having oxygen ion-conductivity;   (b) a pair of metal electrodes formed respectively, on the inner and outer surface of said solid electrolyte vessel;   (c) a sintered mixture of a metal and its metal oxide, which constitutes a reference oxygen partial pressure source within said solid electrolyte vessel and separated from said metal electrodes;   (d) a holder for said electrolyte vessel which is electrically connected to the metal electrode on the outer surface of said solid electrolyte vessel;   (e) an output terminal electrically connected to the metal electrode on the inner surface of said solid electrolyte vessel, and   (f) an electrically non-conductive spacer in said electrolyte vessel disposed between the sintered mixture and the inner surface of the vessel for supporting said sintered mixture both axially and radially of said vessel to prevent movement of said sintered mixture within said vessel due to vibrations of the vehicle, said spacer being of a material which is non-reactive with said metal electrode on the inner surface of the vessel.   
     
     
       2. Oxygen concentration detector as claimed in claim 1, in which said non-conductive spacer is made of a fibrous substance. 
     
     
       3. Oxygen concentration detector as claimed in claim 1, in which said non-conductive spacer is made of a material selected from the group consisting of silica wool, alumina wool and mullite wool. 
     
     
       4. Oxygen concentration detector as claimed in claim 1, in which said non-conductive spacer is made of a sintered inorganic substance. 
     
     
       5. Oxygen concentration detector as claimed in claim 1, in which said non-conductive spacer is made of a material selected from the group consisting of sintered Al 2  O 3 , sintered SiO 2  and sintered mullite.